Free-flight arming device



May 31, 1960 J. RABlNow FREE-FLIGHT ARMING DEVICE 3 Sheets-Sheet 1 Filed July 5, 1956 May 3l, 1960 .1. RABlNow 2,938,461

FREE-FLIGHT ARMING DEVICE Filed July 5, 195s s sheets-sheet 2' IH Wiswwm INVENToR. Jacob Rahinnw .HTTDRNEYS May 3l, 1960 J. RABlNow 2,938,461

FREE-FLIGHT ARMING DEVICE Filed July 5, 1956 3 Sheets-Sheet 3 'IIIIIIII INVENTOR. Jac: :lh Rab-innw V2,933,461 FREE-FLIGHT ARMING DEVICE Jacob Rabinow, Prince Georges County, Md., assigner to Ythe United States of America as represented by the Secretary of the Army The invention described herein may be manufactured or used by or for the Government for governmental purposes without the payment to me of any royalit-y thereon.

This invention pertains to the art of fuzing projectiles such as bombs, rockets, mortar shells and others. More particularly it relates to safety and arming systems Afor projectiles. In projectiles of this type, particularly in the case of bombs, the arming cycle of -a fuze is usually started by the withdrawal of an arming wire or the charging of a capacitor at the instantof bomb release. Serious accidents have occurred inthe past because of the fact that bombs have been accidentally dropped onto airfield runways or decks of aircraft carriers. In such'cases the fuzes .generally complete their arming cycle even though substantial air travel is normally required. The backwash of propellers or of turbo-jet engines operates arming varies of such fuzes and duplicates the conditions encountered in proper drops. In some fuzes provision is made to sterilize the fuze if impact occurs before proper arming in order to avoid this disadvantage. This leads to other troubles since such sterilization schemes may result in duds. For example, a bomb may jostle another bomb accidentally immediately after release or a bombmay -hit a part of the bomb bay upon its release 'from they aircraft and thus cause a dud.

To eliminate these disadvantages and to insure muchgreater safety, the present invention comprises an arming system which makes use of the fact that a bomb or other low velocity projectile in free Hight experiences acceleration of less than l g. I make use of this fact by a special zero g device so connected that the bomb must be free flight for several seconds for 'arming to occur. If vthe bomb employing this invention should accidentally fall upon the deck of a carrier or upon an airfield runwayV it would not arm because it then would Vbe under acceleration of l g or greater. As described more fully herein, the device can be so arranged that accidental jostling of one bomb by another will not permanently disarm the bomb and proper function will result. This invention of arming a bomb or other projectile under conditions of zero-'g or fractional-g may be 'employed in either electrical or mechanical form.

One object of this invention, therefore, is 'an arming system for fuzes adapted to remain inoperative in the 'event the containing projectile is accidentally dropped upon an airfield runway or aircraft carrier deck.

Another object is an arming system adapted to re` nain inoperative in the event the fuze is subjected to an acceleration greater than a predetermined amount occurring subsequent to the expiration of a predetermined time.

A further object is a fuze arming system as aforesaid which will arm even though subjected to an `excessively great acceleration provided that acceleration occurs prior to the expiration of a predetermined time interval.

A still further object is a safety device for fuze arming systems adapted to prevent fuze arming in the event the 2,938,461 Patented May 31, i960 field or aircraft carrier runway. The specific nature of the invention'as well as other objects and advantages thereof |will clearly appearfrom the following description and accompanying drawings in which: Figure 1 is a vertical sectional view of one form vof my safety switch in the normal condition.

Figure 2 is a cross sectional view of the device of Fig. l taken on the lines 2-2 thereof. Figure 3 shows the switch of Fig.l 1 in the actuated condition. e Figure 4 is a view similar to Fig. 2 showing the switch in the actuated condition. Figure 5 is a vertical sectional view of a second forrn of my switch in the normal condition. Figure 6 shows the switch of Fig. 5 in the actuated condition. i-

Figure 7 is a schematic view of an unarmed fuze embodying the arming system of this invention. Y Figure 8 is `a fragmentary view of Fig. 7 showing the fuze in the armed condition.

Figure 9 is a schematic diagram of the electrical circuitry ofthe fuze shown in Fig. 7.` I Figure l0 is a variation of thecircuit of Fig. 9. i

Figure 1l is a schematic view of amechanicalswitch which is the equivalent of the electrical switch of Fig..5 Figure l2 shows the switch of Fig. l1 in the actuated condition. e

Referring now to Fig. 1, a metal electrical conductive housing l supports an insulating member '2 within'the hollow base 2a thereof. Aixed to member 2 centrally thereof and extending upwardly therefrom is terminal A helical spring 4 has its inner end affixed to terminal 3, the outer end of spring 4.having aixed thereto a heavy metal ring 5, the ring being lconcentric with terminali and normally out of contact with all members other than spring 4. Housing k1 is .perforated at 1 a and 1b to prevent electrical contact between housing 1 and terminal ,3, Fig. 3 shows thecontact-established between ring and housing 1 when the fuze is 'under an accelerationof one g or greater acting in a direction upwardly along the surface of the drawing. If one leg of an electrical circuit, not shown in this figure, terminates at housing ,1 and the other leg terminates at. terminal 3, the circuit "will be completed through spring 4 and vring `5 under 'the -condition described.

Figure 4 shows that electrical contact is made under sidewise acceleration (as compared to the upwardv acceleration of Fig. 3). Ring 5 now contacts the side, rather than the base, of housing 1. Referring to Fig. 5, a generally cylindrical lhousing (6 supports an insulating disc 7 which is provided with a cup-like recess '7a in which rests a cylindrical weight I8 axially bored at one end. A tension spring 9 maintains the weight normally in central position by having oneencl thereof affixed to disc 7 centrally thereof andthe other end ailixed to the closed. end of weight 8. l

Fig. 6 shows theaction which Vtakes place whenfthe assembly of Fig. 5 lis accelerated substantially at afright angle to the axis of the weight 8. Spring 9 is extended by the force exerted upon it by weight 8, the weight being permitted to pivot sidewi'se on its base and in so doing "to contact housing 6. Thus, a circuit is Vcompleted through spring 9 and weight 8 vwhen terminated at spring 9 and housing 6. l

While one device such as shown in Figs. 5-and "6 is omnidirectional, two devices Vproperly connected 'and placed at right angles to one another will Arespondto excessive acceleration regardless ofthe direction of the acceleration.

Referring now vto Fig. 7, a fuze ogive 10 has mounted upon it a contact ring 11, insulated from the ogive by a suitable member 12, and connected by wiring 13 to a power supply 14, the powersupply being grounded to the ogive. Power supply 1'4, in Ytu`r1,1,'is connected tov an acceleration-sensitive switch 15. The switch 15 maybe of'atype shown in Figs. l or 5. A Switch 15 is also connectedwith the heating element 16 of an explosive motor 16a' which, when activated, will'cause the expansion of bellows member 16h. The bellows member is so positioned'that expansion thereof will cause linear motion of the safety block 1 7 until that motion is arrested by the stop 18. When such motion has occurred, explosive detonator 19 in aperture 19a of block 17' will be'aligned with aperture 20 in safety plate 21, permitting ignition of the booster charge 22 when tiring pin 23', which is normally biased forwardly by spring 24, is caused to move rearwardly and engage detonator 19 as a result of impact 4 the Fig. 9 circuit capacitor 26 is charged through resistor 27 from capacitor 25 after capacitor 25 has collected a charge from an external source when the projectile is launched.

Now it can be seen that, should a bomb containing a fuze such as that shownin Figs-7, strike the bomb bay of the airplane upon vbeing released, a part, at least, of

the charge upon capacitor 26 will be discharged through one of the switches 29, 29a, which fswitch lwas v'caused to close under an'impact of the bomb with the bomb bay. The amount of charge upon capacitor 26 is small at this time inasmuch asjthe bomb was released only moments beforethe impact occured. Suicient charge of'pinv 23 with a target, not shown. The armed position switches 29 and 29a, which are identical in construction, Y

but whose axes are oriented mutually perpendicular, are

. connected in Vparallel and the combination connected in parallel with capacitor 26. A resistor 30 may be connectedin series with the switches 29 and 29a.

The circuitry of Fig. 10 is a modication of that shown in'Fig. 9. The system of Fig. l0 contains its own power supply 31 which is substituted for capacitor 25 in Fig. 9,. vSafety device 32, shown here in block form, must be placed in series with power supply 31, such as a battery, to prevent the fuze from becoming energized prematurely. Device 32 maybe operated by the'conven'- tional armin'gwire orany other,Y suitable arming device l closed switch as before.

remains upon capacitor 25 to recharge capacitor 26 after the yswitch reopensafter the bomb moves clear of the airplane. Thus, the fuze Vis in condition to function properly upon impact with a target later in its ilight.

Y If, however, the bomb should Yfall upon an airfield runway or upon the-deck of an aircraft carrier as the plane is ascending 'or descending, there is a different result. f One of the switches 29, 29a will close as before.

The charge upon capacitor 26 will discharge throughthe This time, however, capacitor 26 will have drawn from capacitor 25 an amount of charge short of that required to -re diode 28'but suflicient to prevent capacitor 25 from recharging capacitor 26 after the switch reopens upon the abatement of acl celeration of 1 gior greater. remain inoperative and safe.Y Y

Referring now to Fig. 11 it will be seen that agreat similarity exists to the configuration of the device shown in Fig. 5 in that a cylindrical housing 6a is provided The fuze will, therefore,

with a base V'7bA having a cup-like recess 7c inAwhich rest-s i central position shown in Fig. 11.

as known to the art. Contact ring`11 is not required VVwhen, a self-containedv power supply is employedinasmuch as the purpose of 'the ring is to collect 'a charge from an external source. YA resistor 30 may or may not beemployed in series with switches 29 and 29a for reasons discussed hereinafter'.

l Referring'again to Fig. 9,:as fuze ogive 10 and ring ii:

11 are brought into contact with the terminals of a voltV- age source, not shown, upon launching, a charge is placed upon capacitor25. Ths charge leaks to capacitor 26 through resistor 27 until the striking voltage of diode 28 has been reached. Upon the attainment of such voltage, diode 28 res, causing current to ow through heating element 16 ofY explosive motor'16a. If, however,

leither of the switches 29 or 29a should close before firing of the dode 28 occurs, capacitor 26 will discharge through the switch circuit so completed. The time Vre- Vquired for capacitor 26 to assume its initialv charge, to

'plete discharge, and by the resistance of the circuit, which v may be increasedby the addition of a resistor 30 in series with the devices 29 ,and 29a. l

The operation of the circuit of Fig. 10 is identical with the operation of the circuit of Fig. 9 with the exception that power in the Fig. 10 circuit is made availableto i charge capacitor 26 through resistor 27 from power supply 31 upon actuation of safety device 32 whereas in a cylindrical weight 8a axially bored at one end.. A tension spring 9a, one end of which is axed to base 7b and the other end of'which is vaixed tothe closed' end of weight 8a, normally maintains the weight in the In this embodiment, however, it is not necessary'that the housing 6a orfthe weight 8a be conductive,nor that the base 7b be'nonconductive, inasmuch as this device operates upon Vmechanical rather than electrical principles. The weight v8a is connected toa lever.33, pivoted at 33a, by means of a Vmotion transmitting linkage 34, such as a'cordvor cable,"threaded through an'aperturer38 provided therefor in' base 7b. "A detent 3'3b is provided at one end ofl lever 33 to Vengage a tooth 35 on balance-wheel 36 of aY clock-type arming system, not shown.

In Fig; 12 the'deviceis shown being acted upon by an acceleration of l'g or greater directed generally directed perpendicular to the axis of weight 8a. Weight 8a is driven sidewise by this force and in so doing extends the spring 9a. It also exerts a pull upon linkagev 34 which is-caused to move to the right of the drawing.

Lever 33 is caused to rotate counterclockwise about pivot 33a so thatdetent 33b engages tooth 35 andrarrestsV the motion of balancewheel 36;v In this manner fuze arming is delayed during the time the fuze'is Vsubject to an vac-V celeration of at least 1 g. Y Y

It will be understood that the embodiments described herein are exemplary only and thatfot'her modifications may be made without departing from the spirit and scope of the invention as set' forth in the claims. v

What I claim is: 1.'An arming system for projectile fuzes of the type i .wherein an explosivegdetonator is normally misaligned ing means, explosive motor means `adapted to align saidA .explosive v.detonator with said booster charge `and electrically connected to said energy storing means through a normally relatively high resistance path, a normally open low resistance path arranged in parallel with said explosive motor and said normally high resistance path, said explosive motor means adapted to function by drawing its activating energy from said storing means after the energy in said storing means attains a predetermined value, and acceleration sensitive means in said low resistance path adapted to close said low resistance path and thus draw off a portion at least of the energy from said storing means in the event the acceleration acting upon the projectile exceeds a predetermined amount.

2. An arming system for projectile fuzes of the type wherein an explosive detonator is normally misaligned with a booster charge, comprising an electrical energy source, means for actuating said energy source upon projectile launching, a capacitor connected to be charged by said source, a resistor connected to reduce the charging rate of said capacitor, detonator alignment means comprising an explosive motor having `an electrical heating element connected to draw its actuating energy from said capacitor, a diode interposed between said capacitor and said heating element, and an acceleration sensitive electrical discharge device connected in parallel with said capacitor and adapted to remove a portion atleast of the charge from the capacitor in the event the acceleration acting upon said 4projectile exceeds a predetermined amount.

3. The invention according to claim 2 wherein said energy source comprises a second capacitor adapted to be charged from an outside source upon projectile launching.

4. An arming system for projectile fuzes of the type wherein an explosive detonator is normally misaligned with a booster charge, comprising an electrical energy source, means for `actuating said energy source upon projectile launching, a capacitor connected to be charged by said source, a resistor connected to reduce the charging rate of said capacitor, detonator alignment means comprising an explosive motor having an electrical heating element connected to draw its actuating energy from said capacitor, a diode interposed between said capacitor and said heating element, and means responsive to abnormal accelerations experienced by said projectile after said launching to disable said arming system.

5. An arming system for projectile fuzes of the typev wherein an explosive detonator is normally misaligned with a booster charge, comprising an electrical energy source, means for actuating said energy source upon projectile launching, a capacitor connected to be charged by said source, a resistor connected to reduce the charging rate of said capacitor, detonator alignment means comprising an explosive motor having an electrical heating element connected to draw its actuating energy from said capacitor, a diode interposed between said capacitor and said heating element, said energy source comprising a second capacitor adapted to be charged from an outside source upon projectile launching, and means to prevent the arming of said fuze when said projectile is subjected to accelera-tion of value other than that of free flight.

References Cited in the file of this patent UNITED STATES PATENTS 1,774,043 Summerbell Aug. 26, 1930 1,841,983 Ruhlemann Jan. 19, 1932 2,388,691 Horan Nov. 13, 1945 2,398,439 Middlemiss Apr. 16, 1940 2,419,828 Ferris Apr. 29, 1947 2,498,032 Dell Feb. 21, 1950 2,498,040 Jordan Feb. 21, 1950 2,501,082 Oliver Mar. 21, 1950 2,575,071 Rockwell Nov. 13, 1951 2,699,118 Leroy Ian. 11, 1955 2,710,578 Rabinow June 14, 1955 2,831,431 Stevenson et al. Apr. 22, 1958 

